Some motorcycles utilize a chain to transmit power from the motor to the rear wheel. Under some conditions, such as when the distance between the front and rear sprocket is substantial, undesirable chain motion may occur. Undesirable chain motion may adversely affect the operation of the motorcycle and/or result in rider injury.
One solution is to limit the motion of the drive chain through the use of a chain guide. The chain guide limits the deflection of the chain out of the plane of the motor and drive sprockets. Chain guides typically include a metal channel mounted to the frame of the motorcycle and a circular rubber insert through which the chain passes.
The metal shell of prior factory equipped chain guides imparts has the disadvantage that strong impact may permanently deform the chain guide. These deformations may result in contact of the chain with the sides of the internal channel of the chain guide resulting in excessive wearing, or even binding, of the chain.
Plastic chain guides have also been developed, but designing these guides to be strong enough to withstand repeated impacts can result in a bulky and consequently heavy part. Reduction of weight is of paramount importance to riders, particularly in race conditions. However, reducing weight while maintaining strength to withstand repeated sudden impacts is a challenge.